Gastroesophageal tube of the Iguana iguana (Iguanidae): histological description, histochemical and immunohistochemical analysis of 5-HT and SS cells / Tubo gastroesofágico da Iguana iguana (Iguanidae): descrição histológica, histoquímica e análise imunohistoquímica de células 5-HT e SS

The work aims were to describe the histological and histochemical structure of the gastroesophageal tube of Iguana iguana and verify the occurrence and distribution of immunoreactive serotonin (5-HT) and somatostatin (SS) cells. Fragments of the gastrointestinal tract (GIT) of five iguanas were which underwent standard histological and immunohistochemistry technique. Immunoreactive cells for 5-HT and SS were quantified using the STEPanizer. The oesophagus has ciliated columnar pseudostratified epithelium with staining Alcian blue (AB) + and goblet cells highly reactive to periodic acid Schiff (PAS). In the cervical oesophagus, the numerical density of 5-HT cells per unit area (QA [5-HT cells]/µm2) was 4.6x10-2 ± 2.0 and celomatic oesophagus presented QA = 4.0x10-2 ± 1.0. The epithelium of the stomach is simple columnar, PAS and AB +. The cranial and middle regions of the stomach presented (QA [5-HT cells]/µm2) = 6.18x10-2 ± 3.2 and the caudal region, QA = 0.6x10-2 ± 0.2. The SS cells were only observed in the caudal stomach, with numerical density (QA [SS cells]/µm2) = 1.4x10-2 ± 0.9 In I. iguana, variation was observed in terms of the distribution of mucus secretions and the pattern of occurrence of serotonin and somatostatin-secreting enteroendocrine cells in the TGI, which possibly will result in an interspecific adaptive response.

Os objetivos do trabalho foram descrever a estrutura histológica e histoquímica do tubo gastroesofágico da Iguana iguana e verificar a ocorrência e distribuição de células serotonina (5-HT) e somatostatina (SS) imunorreativas. Fragmentos do trato gastrointestinal (TGI) de cinco iguanas foram submetidos à técnica histológica e imunohistoquímica padrão. As células imunorreativas para 5-HT e SS foram quantificadas usando o STEPanizer. O esôfago apresenta epitélio pseudoestratificado colunar ciliado Alcian blue (AB) positivo, com células caliciformes altamente reativas ao ácido periódico de Schiff (PAS). No esôfago cervical, a densidade numérica de células 5-HT por unidade de área (QA [células 5-HT] / µm2) foi de 4.6x10-2 ± 2.0 e o esôfago celomático apresentou QA = 4.0x10-2 ± 1.0. O epitélio do estômago é colunar simples, PAS e AB positivo. As regiões cranial e média do estômago apresentaram (QA [células 5-HT] / µm2) = 6.18x10-2 ± 3.2 e a região caudal, QA = 0.6x10-2 ± 0.2. As células SS foram observadas apenas no estômago caudal, com densidade numérica (QA [células SS] / µm2) = 1.4x10-2 ± 0.9. Em I. iguana, foi observada variações em termos da distribuição das secreções de muco e padrão de ocorrência das células enteroendócrinas secretoras de serotonina e somatostatina no TGI, o que possivelmente reflete uma resposta adaptativa interespecifica.

Osteologia do neurocrânio de Iguana iguana iguana (Squamata: Iguanidae) / Neurocranium osteology of Iguana iguana iguana (Squamata: Iguanidae)

O crânio representa o segmento com conspícuas adaptações que, nos lagartos, podem ser conservativas ou impulsionadas por pressões seletivas. Objetivando subsidiar o conhecimento morfológico dos répteis, fornecemos uma descrição detalhada dos ossos que formam o neurocrânio de Iguana iguana iguana com base na análise de três esqueletos secos de espécimes adultos. O crânio da referia espécie possui características basais entre os lagartos sem o fechamento das aberturas cranianas e formato geral triangular. As estruturas ósseas que formam a base craniana apresentam muitas fusões, principalmente no assoalho. Na face caudal o exoccipital e o opistótico estão fundidos e formam o otoccipital, que contribui para a formação dos terços laterais do côndilo occipital. A parte central do côndilo é formada pelo supraoccipital. Fusões e estruturas esqueléticas presentes em Iguana são similares aos demais lagartos. Não foram descritas autapomorfias no neurocrânio para esta espécie.(AU)

Skull represents the segment with conspicuous adaptations that, in lizards, may be conservative or promoted by selective pressures. The aim of assisting the morphological knowledge of reptiles, we provide a detailed description of the neurocranium of Iguana iguana iguana based on analysis of three dried adult skeletons. The skull of this species has basal characteristics in lizards without closure of cranial openings and general triangular shape. Bony structures that form the caudal base have many fusions, especially on the floor. In the caudal face the exoccipital and the opisthotic are fused and form the otooccipital, which contributes to the formation of the lateral part of the condyle. The central part is formed by the condyle supraocciopital. Fusions and skeletal structures in Iguana are similar to other lizards. There are no autopomorphies in the neurocranium for this species.(AU)

Scanning electron microscopical study of the lingual epithelium of green iguana (Iguana iguana).

During the last few years, green iguanas (Iguana iguana) have turned out to be one of the most popular pets. They are omnivorous. In their way of feeding, this crucial function is performed by capturing of the preys and mostly, this is carried out by the tongue. The role of the tongue is also fundamental during the intra-oral transport and during the swallowing of food. This has been reported in several studies about chameleons, agamids and iguanids, nevertheless published data about the mechanisms of capturing and swallowing the prey, and the morphological descriptions about the tongue epithelium, are scarce. Therefore, the aim of this present study was to analyse the morphology of the lingual epithelium in green iguanas by scanning electron microscopy. Three different areas were demonstrated on the tongue surface: the tongue tip, characterized by a smooth epithelium without papillae, a foretongue, completely covered by numerous closely packed cylindriform papillae, and a hindtongue with conical-like papillae. Some taste buds were recognized on the middle and the posterior parts of the tongue. Different functional roles could be hypothesized for the three tongue areas: the tongue tip could have a role related to the movements of the prey immediately after the capturing, while the middle papillae and the hindtongue could have an important role concerning the swallowing phase.

Evaluation of the use of technetium Tc 99m diethylenetriamine pentaacetic acid and technetium Tc 99m dimercaptosuccinic acid for scintigraphic imaging of the kidneys in green iguanas (Iguana iguana).

OBJECTIVE: To evaluate the use of scintigraphy involving technetium Tc 99m diethylenetriamine pentaacetic acid ((99m)Tc-DTPA) or technetium Tc 99m dimercaptosuccinic acid ((99m)Tc-DMSA) for the determination of kidney morphology and function in green iguanas (Iguana iguana). ANIMALS: 10 healthy iguanas weighing >1.6 kg. PROCEDURE: Renal scintigraphy was performed by use of (99m)Tc-DTPA in 6 of the iguanas and by use of (99m)Tc-DMSA in all 10 iguanas. After the injection of (99m)Tc-DMSA, scans were performed for each iguana at intervals during a 20-hour period. Renal biopsies were performed in all 10 iguanas after the final scintigraphic evaluation. RESULTS: In iguanas, the use of (99m)Tc-DTPA for renal scintigraphy was nondiagnostic because of serum protein binding and poor renal uptake of the isotope; mean +/- SD (99m)Tc-DTPA bound to serum proteins was 48.9 +/- 9.9%. Renal uptake of (99m)Tc-DMSA produced distinct visualization of both kidneys. Renal uptake and soft tissue clearance of (99m)Tc-DMSA increased over the 20-hour imaging period; mean +/- SD renal uptake of (99m)Tc-DMSA was 11.31 +/- 3.06% at 20 hours. In each of the 10 iguanas, ultrasonographic and histologic examinations of biopsy specimens from both kidneys revealed no abnormalities. CONCLUSIONS AND CLINICAL RELEVANCE: Results indicate that the kidneys of iguanas can be evaluated scintigraphically by use of (99m)Tc-DMSA; this technique may be potentially useful for the diagnosis of renal failure in iguanas.

Tempo and mode of evolutionary radiation in iguanian lizards.

Identification of general properties of evolutionary radiations has been hindered by the lack of a general statistical and phylogenetic approach applicable across diverse taxa. We present a comparative analytical framework for examining phylogenetic patterns of diversification and morphological disparity with data from four iguanian-lizard taxa that exhibit substantially different patterns of evolution. Taxa whose diversification occurred disproportionately early in their evolutionary history partition more of their morphological disparity among, rather than within, subclades. This inverse relationship between timing of diversification and morphological disparity within subclades may be a general feature that transcends the historically contingent properties of different evolutionary radiations.

Green iguana nephrology: a review of diagnostic techniques.

There is still much to learn about renal physiology and pathophysiology in reptiles. In the case of the green iguana, initiating causes are often inferred from poor husbandry and nutrition, or extrapolated from histopathologic interpretations made late in the course of the disease, or at postmortem. The link between parathyroid hormone and renal disease in humans has been well documented and, given the high prevalence of clinical (and subclinical) secondary nutritional hyperparathyroidism in iguanas, this certainly warrants further investigation in saurians [31,32,34,35]. Apart from hyperparathyroidism, chronic water deprivation also appears to be a common historic factor. As a foliovore originating from the high humidity rain forests of central and South America, water recovery is not considered to be an adaptive stress in Iguana iguana, and therefore, renal anatomy and physiology are considered to be non-specialized compared to more arid or aquatic reptiles [21]. These arboreal lizards do not voluntarily drink from open water but instead imbibe rain or dew droplets from foliage [2]. Maintaining such a species in low relative humidity with a water bowl from which to drink is likely to both increase insensible water losses and interfere with normal water intake. Appropriate therapeutic decisions (including euthanasia) can only be made following an accurate diagnosis. To date, our diagnoses are based largely upon the structural evaluations of renal histopathology, and renal biopsy remains our most useful tool. However, in the future it may become possible to evaluate renal function by quantifying glomerular filtration rate, proximal tubular secretion, or functional renal mass. Glomerular filtration rate may be estimated by measuring the rate of glomerular clearance of substances from the blood (e.g., iohexol). Phenolsulphonphthalein assays may offer an insight into proximal tubule secretion and renal blood flow.

Organización topográfica y áreas especializadas en la retina de callopistes palluma: capa de células ganglionares / Topographic organization and specialized areas in the retina of callopistes palluma: ganglion cell layer

En este trabajo se analizan la distribución topográfica y el tamaño de los elementos neuronales (células ganglionares y amacrinas desplazadas) ubicadas en la capa 8 de la retina de un saurio chileno, Callopistes palluma, utilizando montajes in toto teñidos con técnica de Nissl. Callopistes palluma presenta una retina afoveada, con un área central donde la densidad de células ganglionares y amacrinas desplazadas es de 20.000 y 7.000 cell/mm², respectivamente. La densidad neuronal cae gradualmente hacia la periferia, extendiéndose en el eje naso-temporal de la retina, estableciéndose para ambos tipos neuronianos una banda horizontal de mayor densidad. En las diferentes zonas de la retina, las células amacrinas desplazadas comprenden entre el 25 y el 30 por ciento de la población neuronal total de la capa 8. El análisis del tamaño celular revela que a nivel del área central se observan neuronas de tamaño pequeño con medianas de 32 µm² para las amacrinas desplazadas. En la retina periférica se aprecia un incremento en el tamaño celular y las medianas suben a 42 µm² y 12 µm² de área celular para las ganglionares y amacrinas, respectivamente. En el texto se discute la correlación entre características retinianas y estilos de caza

Retinohypothalamic projections and immunocytochemical analysis of the suprachiasmatic region of the desert iguana Dipsosaurus dorsalis.

Two separate and distinct retinal projections to the hypothalamus in the iguanid lizard Dipsosaurus dorsalis were described using horseradish peroxidase and cobalt-filling techniques. Both of the projections were unilateral and completely crossed; one terminated in the supraoptic nucleus and the other in the suprachiasmatic nucleus. Immunocytochemical analysis showed that the supraoptic nucleus contained cell bodies and fibers that cross-react with antibodies raised against arginine vasopressin, while the suprachiasmatic nucleus contained arginine vasopressin-like immunoreactive fibers emanating from cells in the nearby paraventricular nucleus. The suprachiasmatic nucleus contained a dense plexus of fibers that cross-reacted with neuropeptide-Y antibody. Antiserum against vasoactive intestinal polypeptide showed no reactivity in any part of the forebrain, while antiserum against serotonin showed sparse and uniform reactivity throughout the forebrain, including the suprachiasmatic nucleus. These results, together with other data, indicate that the suprachiasmatic nucleus of D. dorsalis is homologous to the suprachiasmatic nuclei of rodents, structures known to contain circadian pacemakers. We suggest that the suprachiasmatic nucleus may play a similar role in the circadian system of D. dorsalis.

The organization of central auditory pathways in a reptile, Iguana iguana.

The present experiments were designed to trace the central auditory pathways in an extant reptile, the New Worlkd lizard--Iguana iguana, utilizing anterograde axonal degeneration stained by the Fink-Heimer ('67) method and the retrograde axonal transport of horseradish peroxidase (LaVail and LaVail, '74). Beginning with the projections of the auditory portion of the VIIIth nerve, the ascending pathways were traced through successive relay nuclei to the telencephalon. The auditory portion of the VIIIth nerve projects to two nuclei in the dorsomedial medulla-nucleus angularis and nucleus magnocellularis medialis. These two nuclei together with a third cll group, nucleus magnocellularis lateralis (intercalated between nucleus angularis and nucleus magnocellularis medialis), have been referred to as the auditory tubercle in previous studies (cf. Miller, '75). The axonal degeneration following large lesions of the auditory tubercle and small lesions of nucleus angularis demonstrated the second order auditory pathways. Fibers leave nucleus angularis ventrally and travel to the ventral surface of the medulla where they cross the midline and ascend to the midbrain in pathways resembling the trapezoid body and the lateral lemniscus of mammals. Along these pathways, terminal arborizations of some fibers were seen in three lower brainstem nuclei while other fibers ascent to the midbrain and terminate in the central nucleus of the torus semicircularis. Experiments in which horseradish peroxidase injections were made in the torus semicircularis demonstrated that nucleus angularis is a primary source of second order auditory fibers to the midbrain and, in addition, that two of the lower brainstem targets of the auditory tubercle project to the torus semicircularis. These lower brainstem pathways were shown to be associated with the auditory system by electrophysiologically recording sound-evoked responses from clusters of cells in the torus semicircularis. Ascending fibers arising from the central nucleus of the torus semicircularis were followed rostrally where they entered the dorsal thalamus and terminated throughout nucleus medialis. Finally, a thalamotelencephalic auditory pathway was traced from nucleus medialis into the lateral forebrain bundle. Terminations of this pathway from nucleus medialis were seen in the medial dorsal ventricular ridge and in the striatum. It was concluded that the ascending auditory pathways of the iguana bear a remarkable resemblance to both the mammalian and avian auditory pathways from the level of the first order neurons in the VIIIth nerve to the level of the telencephalon. At the same time, there are important specializations of the auditory system in birds and mammals such as the development of particular lower brainstem nuclei. Nevertheless, a basic plan for the organization of the auditory system in terrestrial vertebrates can be recognized which invites comparisons with the vertebrate classes that remained in aquatic habitats...